1. Field of the Invention
The present invention relates to integrated circuits and pin count reduction.
2. State of the Art
As the integration density of integrated circuits increases, designs have increasingly become pin-count limited. That is, the features to be included in the chip are limited by the number of I/O pins of the final chip package. Furthermore, the cost of the chip package in proportion to the total cost of the typical integrated circuit continues to increase. In many instances, the cost of the final integrated circuit is dominated by the cost of the package. For high-volume integrated circuits, a relatively small savings per part in the cost of the package can result in a substantial overall cost savings. Hence, design efforts to reduce pin count so as to allow a lower-cost package to be used instead of a higher-cost package are of considerable importance.
Consumer electronics devices are high volume and very cost-sensitive. An example of one such device is a game player. A game player may have diverse memory devices such as a boot ROM (Read Only Memory) and a CD ROM drive, DVD drive, or the like. A system controller for such a device must interface to both types of memory devices. CD ROM drives and the like are typically IDE (Integrated Device Electronics) devices conforming to the IDE standard. Whereas ROMs typically reside on the same printed circuit board as the system controller, IDE drives are connected to the printed circuit board using a cable. Pin sharing between the memory devices is problematic in that if the devices are connected to the same pins, the ROM will have insufficient drive strength to drive the pins.
Furthermore, the pin requirements of the devices are substantially different. An IDE device has a wide data bus (e.g., 16 bits) and a narrow address bus (e.g., 3 bits). A ROM, on the other hand, has a narrow data bus (e.g, 8 bits) and a wide address bus (e.g., 16 bits). The disparate nature of these memory devices therefore renders pin sharing extremely difficult.